1. Technical Field
The present invention relates to a packaging unit used for packing products such as drugs, foods, cosmetics and the like, and particularly to a packaging unit employing a tamper-proof technique.
2. Background Art
In the field of drugs and foods, package boxes are conventionally known which include an openable portion for breaking and removing a seal of a lid by a push-in operation. One example of such package boxes is disclosed in Utility Model Publication No. 50-33370 in which an openable and closable paper lid having an insert piece is formed integrally with an opening edge of a paper box body. Tear-aiding perforations are formed along peripheries of a wall portion of the package body overlapping the insert piece of the lid in a closed position and also joined to a predetermined position of the insert piece by an adhesive agent. These perforations define a punch-out portion that serves as an openable portion for breaking and removing the seal of the lid by a push-in operation.
This package box has one advantage that whether the package box has already been opened or not may be recognized easily based on whether or not the punch-out portion is broken along the perforations, and another advantage that the opened package box may be used as a storage case for the product since only part of the wall of the package body is broken. On the other hand, the package box is exposed outside before it is opened, and it is possible for the adhesively joined portion between the punch-out portion and the insert piece of the lid to be broken and opened with skill from outside. Thus, the conventional package unit remains unsatisfactory from the viewpoint of tamper-proofness.
It may be possible to seal and pack a package box having an openable portion as noted above with a heat shrinkable film utilizing the film packing technique disclosed in Unexamined Patent Publication No. 7-137721, for example, and to form unsealing perforations in the film beforehand.
In this case, since the openable portion of the package box cannot be tampered unless the film sealing and packing the package box is removed, the tamper-proof effect can be enhanced. However, a disadvantage of complicating an unsealing operation is caused by requiring a step of tearing the film along the perforations and a step of breaking and removing the seal of the lid by pushing in the openable portion of the package box. Further, the unsealing operation is time-consuming since this tends to involve the trouble of locating and tearing the perforations formed in part of the film.
The smaller the length of the perforations formed in the film, the less is the possibility of tearing and damaging the perforations due to an external force applied to the film in time of distributing and displaying the product. At the same time, there occurs a problem of increasing the trouble of locating the perforations when removing the seal.